Could you clarify Peace4U. Your question was about US deserters, but surely any 'betrayal', 'dishonouring a commitment' and the like applies to any deserter, not just a US one? Given that Canada's decision was not to join the coalition, what would justify treating US deserters differently from say Russian, Liberian or even Iraqui deserters?
A quick Gooogle reveals 1) Only Congress can declare war. 2) They didn't. So 3) these guys can't quite 'desert in the face of the enemy'. And, given that the President's executive decrees—one could argue unconstitutional decrees—have already cost the lives of many of their comrades, and that Mr. Bush is a guy determined to keep those he has declared 'enemies' locked up indefinitely, without charges or legal review, (can you say lettres de cachet, Star Chamber, Inquisition, oubliette?); it's not hard to imagine concluding, "This country, and its armies are in the hands of a dictator—who's gonna get me killed. Illegally. This is not the army I joined".
And let's not think of what put him in the Oval Office.
It does feel good to jerk your knee when it gets rapped, but there's a vastly greater amount that has to be processed when organs of thought are involved. For Canada the issue is simply: Does this person meet the requirements for entry as a visitor, refugee, or immigrant, or are they are properly accused of any crime subject to extradition treaties? Find "US deserters" in there, and I'm with you.
But until both counties are at war—the same war—I bet you can't.
Furthermore, if you're proposing to turn away all deserters, why that's a pretty simple bit of wording I'm sure you can come up with. But beware if you're tempted to allow exceptions—like a deserter from a death squad—or add other offenses, escape clauses or definitions, because that's where legalese, lawyers and appeal courts are born. Real life is harder than a coupla sentences on TERB.
So I'm told; how would I know?